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I’ve had a small number of issues with brass inserts and at least one failure using barrel nuts. All of it is related to end grain issues. While trying to figure out a barrel nut failure (wood pulled out), I realized that either technique was dependent on end grain integrity in the tenon. Before carving the tenon, why not splice vertical grain wood at tenon? Glue and screw, then rout the tenon. U can use either the insert or barrel nut. Reduce issues of pullout. I see no downside to this, and nothing but upsides. Thoughts? (I rout my M&T after body built)

Sounds a lot like the Martin "applied dovetail" to me--makes sense. I've had a couple of problems with brass inserts (my usual way of attaching necks), but have learned how to get around the endgrain issues for the most part.

It's not a pretty solution, but really hanger bolts put into the heel/tenon the way that Gibson and other banjos are done (and some guitars too), and using a nut to attach the neck seems a lot more practical than any of the barrel nut/insert options. Hanger bolts hold on to the endgrain just fine, they're just not very attractive inside the instrument.

Dave

That's basically what I learned to do from Rick Davis some years ago. The tenons on my necks have a cross-grain insert. (I use barrel nuts.)

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I use a simple butt joint and insert, so I hesitate to comment on the M&T type bolt on, but two things I do is use the "broken thread" zinc inserts rather than the brass type (they bite deeper and allow more space for the wood) and secondly I saturate the end grain with thin super glue around the insert.

If/when I use bolted necks again (currently on a dovetail kick), I will probably use something like the Gore/Gilet method of installing a threaded square metal bar in the heel. Since the square metal bar has a flat face instead of the round face of a barrel nut, it doesn't have the same wedging action as a barrel nut. And it doesn't rely on end grain to hold the threads of an insert. It might be a bit of a hassle to install if one doesn't have a mortising machine, but installing cross-grain bits of wood takes extra work, too.

Just an idea to ponder.

Mike, I see no reason why your suggestion wouldn't work and I don't see any downside in doing it.

I've had a failure with the Collins-style hanger bolts and several with brass inserts. Luckily all failed before they went out the door of the shop. Haven't had a failure with barrel nuts.

Eventually I went to the Gilet/Gore bolt-bar method, which I find stronger and less prone to failure than the other three. I mention it because unlike the hanger bolt or insert methods, it is unlikely to fail due to issues with endgrain and also avoids the risk of a barrel nut splitting the tenon via a wedging action (I've heard about this happening but it never actually happened it me - is that what happened with your barrel-nut failure? )

The bolt-bar takes a little longer to execute than say installing a pair of brass inserts or hanger bolts, but it lets me avoid the additional work that I ended up doing as insurance for those other methods (for example gluing a vertical dowel in the heel so you aren't screwing your bolts into end grain etc). For me it ends up being a wash in terms of time spent.

I see Josh and I are sharing the same brain. Your turn, Josh.

Don, I think we posted within 30 seconds of each other about this method

Access to a chisel mortiser is ideal but I don't have one; I use one of the generic drill-press attachments similar to https://www.rockler.com/rikon-morticing ... -w-chisels

Mine was a bit cheaper as it came without any chisels; I bought the 3/8 chisel I needed off ebay separately.

Regardless, barrel, insert, capping the end grain makes sense to me. End grain has no real lateral support for an insert and zero vertical support for a barrel nut.

On my next neck, I’ll post pics of what I’m doing

Saw something I want to try. Drill a 3/8" hole down the heel from under the fretboard to under the heel cap (before either is installed) and glue in a 3/8" hardwood dowel. Now you have side grain for the threaded insert to live in.

Ed

I tried a tenon joint once and had problems with the tenon splitting as mentioned above. I use a butt joint with 2 steel inserts (1/4-20 inner threads, 5/16” barrel not counting the threads). Before installing the inserts, I glue a half inch maple dowel with the center a half inch in from the edge so that the insert grips a quarter inch into the dowel. I put a drop of ultra thin CA on the outside edge of the insert so it won’t turn out if the bolt is unscrewed. No failures so far in well over 100 guitars. The hanger bolts seem much more solid (and I have used them when I want the neck attachment to hold more than the normal load), but they are in the way if I want to floss the joint.

This is exactly how I did mine when I was using this method-I never had a problem with it.

I used 1/2" hard maple dowels.

That’s similar to what I do. When I have the end of the Neck squared up I use a table saw to mill two 1/8” slots just inside the width of the tenon that go deep enough to go a little under the heel cap. Then glue in some snug maple cross grain splines. When dry I drill for the bolts an cut the tenon as normal. It works great and doesn’t take much time.

With regard to your original post I’m not sure about the screws you mention

I do the same joint and use a maple dowel in the heel with the flat grain perpendicular to the bolt holes to screw the inserts. I like using those zinc ones too as they have a Allen key head which makes it easier. But I have used brass many times too and never had a problem. I think with a dowel you can use what ever you want.

This is what I do for barrel bolts when I do a bolt on. Really fast, just a saw kerf and very strong. Most of the time I use a dovetail.

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Steve Smith
"Music is what feelings sound like"

For my travel guitars I drill a hole in the heel for a dowel and split the dowel and insert a metal plate between the halves. I use a 10- 24 socket head cap screw through the heel and the head bears against the metal plate. The metal plates I get from the "economy" draw bolt fasteners, one of which is threaded and one of which has no threads and allows the 1/4 - 20 bolt to pass through. I use the non threaded one for the travel guitars, but a person could install the threaded one in the doweled heel and use a furniture connector bolt to attach the neck.

https://woodworker.com/tite-joint-faste ... 99-048.asp

I have been using a reinforced tenon for the barrel nut attachment technique for 10 -12 years. I did some testing and with maple reinforcing bars the testing rig broke before the I could get the tenon to break.

Without them it broke fairly easily. Don’t use the Cumpiano attachment tech without reinforcement.

Here is a good thread on the subject.

viewtopic.php?f=10101&t=31203&hilit=Cumpiano+neck+bolts

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Thanks everybody. Lots of great ideas, learned a lot here!

I forgot to mention, I had one of my early guitars from around 2004 come back for a neck refinish. It had the barrel nut attachment but I was not reinforcing the tenon then. The owner who is a touring folkie doing hundreds of gigs a year didn't think there were any issues and it looked good.

When I took the neck off the lower barrel nut area was cracked but holding. Had to reinforce it with the fretboard on which took some brainstorming but I came up with a router jig that worked using the small Stewmac base and a Dremel.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Im goning with a pre-bond hardwood cross grain glue on strip, 1/4 " thick min. I will then rout the tenon. Someone asked about screws, I am using #4 1/2" screws to do the clamping. Barrel or insert, this should never fail.

After you do this, could you post a photo? I'm having a hard time picturing what you have in mind.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

in 20 years never had an issue maybe it is the brass inserts your using post links of what you are using

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

John,

I thought your primary joint was the dovetail?

Mike

I do 90% dovetail but I also deal with bolt ons with Martin.
There are a number of inserts out there I use the same ones Martin does and I have not seen a failure in normal use
I have seen some from damage. I use a 5/16 hole
if you have a tenon failure you are using the wrong insert. I use these on 3/4 in tenons my tenon is 5/8 deep so I am getting some of the insert into the heel

https://www.hillmangroup.com/us/en/Fast ... %29/p/3019

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it